There is a need in the electronic equipment industry for means for making convenient and secure electrical connections to sets of small side-by-side terminal pads, such as the terminal pads of a printed circuit board or a liquid crystal display. A promising technique for making such connections is taught in laid-open United Kingdom patent application No. 2,048,582A, filed Mar. 18, 1980 and published Dec. 10, 1980, which teaches an adhesive connector sheet material comprising a flexible insulative sheet, a plurality of parallel, separated, electrically conductive stripes carried on the sheet, and an electrically conductive adhesive covering the conductive stripes. Electrical connections can be made by adhering an end of the sheet material against a set of terminal pads, with individual stripes on the sheet material in alignment with individual pads.
For satisfactory use of sheet material as described, the electrically conductive adhesive in the sheet material must achieve a low-resistance bond that is stable for the length of time and under the operating conditions that are expected for the sheet material. Conventional electrically conductive adhesives have not provided the needed degree of stability and low resistance. Initial resistance is too high and/or resistance increases during use, to the extent that mechanical clamping techniques are often used to supplement the adhesive bond.
Also, a disadvantage of the described connector sheet material is that the electrically conductive adhesive covering the stripes can unintentionally be brought into contact with other members of an electronic assembly at intermediate portions along the length of the sheet material, thus introducing undesired electrical connections into the assembly. Such unintentional contacts could be avoided by covering the intermediate portion of the sheet material with an insulating layer, as has been done with some miniature flat cables of the prior art (see U.S. Pat. No. 4,113,981 which describes a cable comprising a flat sheet carrying electrically conductive stripes). However, such an intermediate covering of a cable is inconvenient and uneconomic, since it requires applying insulating material in specific lengths for specific uses. Application in specific lengths is a more difficult operation, and it requires maintaining an inventory of cables of different insulated lengths for different jobs. Alternatively, insulation must be removed from the end portions of the cable, which is difficult and not adapted to speedy automated operations.